1. Technical Field
The present invention relates to an arm stopper mechanism for inhibiting a turning angle of a pitman arm mounted with a tie rod, and an electric power-steering device using such an arm stopper mechanism.
2. Related Art
For example, with a saddle-ride type vehicle such as an all terrain vehicle (ATV), the electric power-steering device is interposed between a steering shaft on the side of the steering wheel and a steering member on the side of the wheels (front wheels). The electric power-steering device is a device which assists, by using the torque generated by an electric motor, the steering force applied by the driver to the steering wheel.
The electric power-steering device incorporates members such as an input shaft, a torsion bar, and an output shaft. The input shaft is coupled to the steering shaft on the steering wheel side. The torsion bar is coupled to the input shaft and the output shaft. A pitman arm is mounted on the output shaft (for instance, refer to JP-A-2007-196927 (FIG. 2)).
A pitman arm is a steering member on the side of the wheels (front wheels). The pitman arm is provided with tie rod holes to which tie rods are mounted. The wheels are coupled to the tie rods. The pitman arm is configured to turn about the output shaft.
When the driver attempts to turn the steering wheel beyond the maximum steering angle in the clockwise direction or the counterclockwise direction, the electric power-steering device needs to restrict the turning of the steering wheel so that the vehicle will not fall over. As a mechanism for preventing the foregoing fall-over, the electric power-steering device is provided with an arm stopper mechanism which restricts the turning angle of the pitman arm with a stopper.
The stopper is provided in a manner of protruding in a downward direction from the lower face side of the housing of the electric power-steering device. When the driver attempts to turn the steering wheel beyond the maximum steering angle in the clockwise direction or the counterclockwise direction, the arm stopper mechanism is configured such that the abutting faces provided to the pitman arm are abutted to the contact faces of the stopper. Thus, the arm stopper mechanism restricts the turning angle of the pitman arm using the stopper and consequently restricts the turning of the steering wheel.
With this kind of electric power-steering device, when the bending load that is applied to the output shaft increases, since the output shaft is coupled to the steering wheel via the input shaft, the torsion bar and the steering shaft, the steering wheel will vibrate and cause the steering to become difficult. Accordingly, with an electric power-steering device, it is desirable to inhibit the bending load that is applied to the output shaft.